the list looks pretty solid, although i'm scratching my head at how the blazes you fit that into 1000 points. Any how here is little on what i think, one unit unit at a time.

But before that, a note of heavy weapons: mortars are cheap goodness, lascannons are an near necessity (depending how you deal with armor/monsters) and heavy bolters are pretty handy. Missile launchers have there uses but should be left on the side lines, but autocannons and the other hand are your workhorse. with a decent strength and shot output they can be pretty nasty, i recommend atleast half of your hvy weapons to be autocannons.

simple and effective, your better of keeping this guys in the rear guard so avoid taking things that would make you want to move them up, like those G. Launchers. A heavy weapon team is sound but i'll caution against the missile launcher, but it doesnt really matter at this point. Give them the chimera

good good but time for some choosing, on one hand: them vox caster are now useful, but on the other they are soaking up points (no matter how few) were you could place them elsewhere (vets). for example you could give each squad a special weapon guy and add to your mobile fire power for when sitting and shooting isnt favorable (or you could leave them naked, no biggy)

sonu236 makes alot of really good points for this list. Auto cannons galore in the squads and a grenade happy PCs are solid choices. Giving your line squads an auto cannon and a grenade launcher would help them out alot.
I would drop the vox net entirely for a Regimental Standard. Then with a lascannon in your CCs you have a strong orders giving unit that can deal out some support on it's own.
The storm troopers can support the Demolisher but they do need some special weapons. I'd use plasma just to cross the middle ground between the Demolishers H flamer and the cannon.
The 40 pts you have invested in the sentinel I fear are a bit wasted. It's your only scout unit so it's up front and unsupported if it's on the table to start with. Or flanking it reduces the crazy effeectiveness of flanking autocannon. Sentinels are really cool but in this list I'd drop it entirely to free up some points.
For the veterans it seems like they're being deployed in a similar way to the platoon and if that's the case just use two more Infantry squads. Or dump the PCs and just have four line veteran squads backed by the CCs. For this dump one of the squads and kit the other in your chimera with triple melta. Lots of people are incensed by this but it is really effective and fills a niche that is lacking in your list currently. Fast moving anti-tank, objective grabbing cannot be denied and veterans flourish in this use.
Lastly the LRBT needs some sponsons. I'd set it up with the infantry to give your CCs cover. Let the squads support it and keep it from getting deep struck. Then give it HB sponsons and go to town.

How is a Regimental standard better than a vox network?
I am very new to the gaurd so im just wondering why

also would my CCS be more effective if i gave it 4 special wepons as oppsed to a vox and missile launcher
if i gave them like grenade launchers or plasma gus i would march them up with my Vet squads. in time i am planning on givving each vet squad a chimera aswell